The drugs issue that seemed to have fizzled out of the US presidential campaign almost before it started returns today with claims in a new biography of Al Gore that the vice-president was an enthusiastic cannabis user in the 1970s.

"We'd get stoned and talk about what we would do if we were president," John Warnecke, an old friend of Mr Gore, is quoted as saying in Inventing Al Gore: A Biography.

An extract from the book by Bill Turque, Newsweek's Washington correspondent, appears in this week's issue of the magazine. It comes at a time when the vice-president had appeared to be seeing off the challenge of Bill Bradley, the only other candidate for the Democratic Party nomination to run for president.

Rumours about the alleged drug use of the young George W Bush, who is fighting for the Republican nomination, subsided late last year after the withdrawal of a book that included discredited claims.

Previously, Mr Gore had said his cannabis consumption was "infrequent and rare". But Mr Turque's book also quotes another Gore friend, Andy Schlesinger - like Mr Warnecke and the vice-president, a former reporter on the Nashville Tennessean - as saying he smoked with him "at least a dozen times". This was in the months after Mr Gore returned from the Vietnam war in 1971.

"These were low times," says Mr Schelsinger, who remains a friend. "Al was upset and disgusted by Vietnam and what it was doing to America."

Mr Turque writes: "Warnecke and two other friends from Gore's Nashville days say Gore was an enthusiastic recreational user, smoking sometimes as often as three or four times a week; after hours at Warnecke's house, on weekends at the Gore farm or canoeing on the Caney Fork River."

Mr Warnecke, who had drink and drug problems that wrecked his first marriage, says Mr Gore tried in 1987, while running for vice-president, to stop his friend from revealing the cannabis use.

In November 1987, after Mr Gore had gone public about infrequent use, Mr Warnecke received a call from a reporter on his former newspaper. But he did not follow his old friend's request, says the book.

"Instead he told what he now says was a more authentic-sounding lie that he'd seen Gore smoke only once. Gore considered even this sanitised version of the past a betrayal and the two have not spoken since 1987."